A 38-year-old man with opioid use disorder describes continued cravings and drug-seeking behavior despite completing medically supervised withdrawal three months ago. He reports that environmental cues such as passing by his former dealer's neighborhood trigger intense urges to use. His PMHNP is reviewing the neurobiology of reward circuitry and addiction to explain why abstinence alone does not resolve the disorder. Which of the following best describes the neurobiological basis of this patient's persistent cravings and cue-triggered drug-seeking behavior?